JP2000126893A - Flux-cored wire for self-shield welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flux-cored wire for self-shield welding in which a weld metal excellent in welding workability and antipermeability, and high in toughness. SOLUTION: A flux-cored wire for self-shield welding in which the flux is filled in a steel shell, contains, by weight to the total weight of the wire, 0.01-0.30% C, 0.01-0.30% Si, 0.50-3.00% Mn, 0.001-0.25% Mo, 1.0-3.0% Ni, 1.5-4.0% Al, 0.5-2.0% Mg, 3.0-7.0% one or two or more kinds of Ca, Sr and Ba, 0.05-0.30% Li, and 0.5-3.0% F, and the ratio Ni/Mo is 10 to 300.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux cored wire for self-shielding welding, and more particularly, to a flux cored wire for self-shielding welding.
The present invention belongs to a technical field related to a flux cored wire for self-shielded welding capable of obtaining a weld metal having excellent welding workability and porosity resistance and having high toughness.
In addition, the porosity resistance refers to the degree of difficulty of the porosity remaining in the weld metal.

[0002]

2. Description of the Related Art A flux cored wire for self-shielding welding (hereinafter also referred to as a self-shielding welding wire) is mainly used in civil engineering and construction fields because of its simplicity that welding can be performed without using a shielding gas. It has been. However, the conventional self-shielding welding wire has poor welding workability and low toughness of the obtained weld metal as compared with a normal semi-automatic welding wire using a shielding gas.

For this reason, efforts have been made to improve welding workability and increase toughness. However, a self-shielding welding wire that can achieve both improvement in welding workability and high toughness has not yet been developed.

[0004] For example, recent studies have shown that patent no.
There is a self-shielding welding wire described in Japanese Patent No. 4403. However, even with this self-shielding welding wire, welding workability is not satisfactory, and the toughness of the weld metal cannot be as high as described in this patent publication. Therefore, the use of the weld metal in a portion where the required value of the mechanical performance is high is restricted, and it has not been widely used.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and provides a weld metal having excellent welding workability and porosity resistance and having high toughness. It is an object of the present invention to provide a flux cored wire for self-shield welding that can be used.

[0006]

Means for Solving the Problems (1) The inventors of the present invention have conducted studies to solve the above-mentioned problems and achieve the object. As a result, as a factor for improving the porosity resistance, the present inventors have found that It was found that it was important to fix nitrogen, reduce the partial pressure of nitrogen in the arc, and suppress the nitrogen dissolution reaction in the molten metal. Furthermore, as a result of studying the raw materials (elements to be contained) that most effectively contribute to each factor, Al was used to fix nitrogen in the weld metal, and Mg was used to reduce the nitrogen partial pressure in the arc.
It was found that Li was effective in suppressing the nitrogen dissolution reaction in the molten metal.

(2) Also, as a result of research on raw materials (additional elements) contributing to welding workability, it was found that the higher the amount of Al added, the more the arc stability and the amount of spatter generated were reduced. It has been found that the addition of Ba leads to stability of the arc, and the addition of F leads to a reduction in the amount of spatter.

(3) Further, it has been found that the addition of elements such as Ni, Mn, C, and Mo can increase the toughness of the weld metal. The details will be described below. As described above, the addition of Al is effective in improving porosity resistance and welding workability. However, the larger the amount of Al added, the more Al
Was found to significantly reduce the toughness of the weld metal. As a result of examining the cause in detail, the solid solution of Al in the weld metal makes the ferrite stable,
It has been clarified that the toughness is deteriorated because the coarse δ ferrite generated during solidification remains after cooling.

[0009] Generally, coarse δ ferrite is formed in the steel weld metal during solidification, but it is once completely transformed into austenite and further transformed from austenite to fine ferrite in the subsequent cooling process. Finally becomes fine and the toughness becomes good. Therefore, even when Al forms a solid solution in the weld metal, it has been found that in order not to deteriorate the toughness, the δ ferrite should not be left, and conversely, it should be completely transformed into austenite. .

[0010] Then, an improvement measure for preventing such δ ferrite from remaining was examined. As a result, it has been found that the balance of the matrix composition of the weld metal is important in order not to leave the δ ferrite. That is, more specifically, in order not to leave δ ferrite,
As described above, it is only necessary to once completely transform into austenite during the cooling process, but this is determined by the matrix composition in the weld metal, and when there is a large amount of Al for stabilizing ferrite, Ni, M for stabilizing austenite is present.
It was found that adding an appropriate amount of elements such as n and C was effective.

Also, in addition to the presence or absence of δ ferrite,
It was also found that the transformation structure from austenite had an effect, and it was also found that by adding a small amount of Mo, the transformation structure from austenite was refined and the toughness of the weld metal could be further improved.

(4) Further, as a result of studying the weld metal composition for completely transforming to austenite by thermodynamic analysis and experiment, when the value of FP determined by the following equation is 0 or more, it is completely transformed into austenite. I found out to be perverted. That is, it was found that the toughness of the weld metal can be further increased by setting the weld metal composition to FP ≧ 0.

FP = [C] −0.145 × [Si] + 0.013 ×
[Mn] −0.3 × [Al] + 0.196 × [Ni] − 0.123 × [M
o] +0.393 where [C] is the C concentration (% by weight),
[Si] is Si concentration (wt%), [Mn] is Mn concentration (wt%), [Al] is Al concentration (wt%), [Ni] is Ni concentration (wt%), and [Mo] is Mo concentration. (% By weight). In each case,
It is the concentration (% by weight) based on the total weight of the wire (the total weight of the flux and the steel sheath).

The present invention has been completed on the basis of the above research results, and is a flux cored wire for self-shielding welding according to claims 1 to 3, which has the following configuration.

That is, the flux cored wire for self-shielding welding according to the first aspect of the present invention is a flux cored wire for self-shielding welding obtained by filling a steel sheath with a flux, wherein C: 0 with respect to the total weight of the wire. .0
1 to 0.30% by weight, Si: 0.01 to 0.30% by weight, Mn: 0.50 to 3.00% by weight, Mo: 0.00
1 to 0.25% by weight, Ni: 1.0 to 3.0% by weight, A
l: 1.5 to 4.0% by weight, Mg: 0.5 to 2.0% by weight, one or more of Ca, Sr, Ba: 3.0 to 3.0%
7.0% by weight, Li: 0.05 to 0.30% by weight, F:
0.5-3.0% by weight, and Ni / Mo: 1
A flux cored wire for self-shielding welding, characterized in that the number is 0 to 300 (first invention).

The flux cored wire for self-shielding welding according to claim 2 has a C content of 0.01 to 0.15% by weight, a Mo content of 0.01 to 0.10% by weight, and a Ni content of 1.4 to 100%.
The flux cored wire for self-shielding welding according to claim 1, which is 2.7% by weight (second invention).

According to a third aspect of the present invention, there is provided a flux cored wire for self-shielding welding, wherein F is defined by the following equation (1).
The flux cored wire for self-shielding welding according to claim 1 or 2, wherein P is 0 or more (third invention).

FP = [C]-0.145 x [Si] + 0.013 x [Mn]-0.3 x [Al] + 0.196 x [Ni]-0.123 x [Mo] + 0.393 ------- 1)

According to the flux cored wire for self-shielding welding according to the present invention, the above-mentioned problems can be solved and the object can be achieved. That is, according to the flux cored wire for self-shielding welding according to the first invention, welding workability and porosity resistance are extremely improved, and a weld metal having high toughness can be obtained. According to the flux cored wire for self-shielded welding according to the second invention, a weld metal having a high level of toughness can be obtained more reliably. According to the flux cored wire for self-shielded welding according to the third invention, it is possible to more reliably obtain a weld metal having a high level of toughness.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is embodied in the following manner, for example. The flux is filled in a steel sheath and drawn. At this time, C: 0.01 to 0.30% by weight, based on the total weight of the wire (the weight of the flux and the steel sheath),
Si: 0.01 to 0.30% by weight, Mn: 0.50 to 0.5%
3.00% by weight, Mo: 0.001 to 0.25% by weight,
Ni: 1.0 to 3.0% by weight, Al: 1.5 to 4.0% by weight, Mg: 0.5 to 2.0% by weight, Ca, Sr, Ba
One or more of: 3.0 to 7.0% by weight, Li:
0.05 to 0.30% by weight, F: 0.5 to 3.0% by weight
And Ni / Mo: 10 to 300. Then, a flux cored wire for self-shielded welding according to the present invention is obtained.

The reason for limiting the numerical value of the flux cored wire for self-shielding welding according to the present invention (first invention) will be described below.

C is one of the austenite stabilizing elements and has an effect of suppressing the remaining δ ferrite and an effect of improving the strength of the weld metal.
If the amount is less than 1% by weight, the effect of suppressing the residual δ ferrite cannot be ensured. Therefore, C:
The content is 0.01 to 0.30% by weight.

Si has the effect of improving the viscosity of the weld metal and the shape of the weld bead, and is a solid solution strengthening element and also a ferrite stabilizing element. Si: 0.
If it is less than 01% by weight, the shape of the weld bead becomes unstable,
If i: more than 0.30% by weight, the strength becomes too high, causing a decrease in toughness. From this point, Si: 0.01 to
0.30% by weight.

Mn is one of the austenite stabilizing elements similar to C, and has the effect of suppressing the remaining of δ ferrite, and also has the effect of increasing the toughness of the weld metal by making the transformation structure from austenite fine. Is Mn: 0.50
If less than 10% by weight, these effects are not exhibited, and Mn: 3.
If it exceeds 00% by weight, the strength becomes too high and the toughness is deteriorated. Therefore, Mn is set to 0.50 to 3.00% by weight.

Ni is one of the austenite stabilizing elements and has the most effect of suppressing the remaining δ ferrite. However, if Ni is less than 1.0% by weight, the effect is not exhibited, and Ni is 3.0% by weight. %, The strength is significantly increased and the toughness is deteriorated. Therefore, Ni: 1.0 to 3.0% by weight
And

Al has the effect of increasing the stability of the arc, reducing the amount of spatter generated, and improving the workability of welding.
It also has the effect of fixing nitrogen in the weld metal and suppressing the generation of pores. From such a point, Al is the most important element. However, if the Al content is less than 1.5% by weight, these effects cannot be obtained. If the Al content exceeds 4.0% by weight, coarse δ ferrite precipitates in the weld metal, and the toughness deteriorates. Therefore, the content of Al is set to 1.5 to 4.0% by weight.

Since Mg is a high vapor pressure metal, it is easily vaporized in a high-temperature arc. As a result, the nitrogen partial pressure in the arc is reduced, the amount of nitrogen dissolved in the weld metal is reduced, and the generation of pores is suppressed. However, if the content of Mg is less than 0.5, the effect is not exhibited. If the content of Mg is more than 2.0% by weight, Mg explosively evaporates, so that the arc is disturbed and welding workability is deteriorated. From this point, Mg is set to 0.5 to 2.0% by weight.

Each of Ca, Sr, and Ba has the effect of improving the stability of the arc, reducing the amount of spatter, and improving the welding workability, and also contributes to the formation of slag. It also has the effect of stabilizing the bead shape. However, the total amount of Ca, Sr, and Ba added is 3.0.
If the content is less than 7.0% by weight, these effects cannot be obtained.
If it is excessive, the stability of the arc deteriorates, and the bead shape becomes unstable due to the increase in the viscosity of the slag. From this point, one or more of Ca, Sr, and Ba: 3.0 to 3.0
It is 7.0% by weight. These elements are usually added in the form of fluoride, carbonate, or oxide, and the effect is the same when any of these elements is used. In particular, it is preferable to add in the form of fluoride.

Since Li lowers the melting point of slag, lowers its viscosity, and lowers the interfacial energy with the weld metal, it uniformly covers the surface of the weld metal and the surface of the droplets.
Suppresses nitrogen dissolution reaction in weld metal. However, Li:
If the content is less than 0.05% by weight, the effect is not exhibited.
If it exceeds 0.30% by weight, the arc is disturbed and welding workability is deteriorated. Therefore, Li: 0.05 to 0.30% by weight. Note that, as the Li source, there are an alloy and a composite oxide, and the most preferable is a composite oxide such as lithium ferrite.

F has the effects of improving the stability of the arc, reducing the amount of spatter generated, and improving the workability of welding.
When the content of F is less than 0.5% by weight, the effect is not exhibited.
If the content exceeds 3.0% by weight, the arc is disturbed and welding workability is deteriorated. Therefore, the content of F is set to 0.5 to 3.0% by weight.
Various fluorides can be considered as the F source.
Fluorides with Sr, Ba, etc. are most preferred.

Mo has the effect of increasing the toughness by refining the transformed structure from austenite, but Mo: 0.00
When the content is less than 1% by weight, the effect is not exhibited, and Mo: 0.2
If it exceeds 5% by weight, the toughness is deteriorated due to the increase in strength. Therefore, Mo is set to 0.001 to 0.25% by weight.

As described above, Ni is an austenite stabilizing element and has the effect of suppressing the residual δ ferrite and increasing the toughness. On the other hand, Mo has the effect of making the transformed structure from austenite fine and increasing the toughness. , M in the first place
Since o is a ferrite-forming element, it tends to hinder the stabilization of austenite of Ni. If the ratio between the Ni content and the Mo content (Ni / Mo) is less than 10,
Austenitization is insufficient because Mo is too much relative to Ni, and sufficient toughness cannot be obtained.
If it exceeds 00, the amount of Mo is too small for refining the transformed structure, and sufficient toughness cannot be obtained. Therefore, Ni / Mo:
10 to 300.

As described above, the contents of C, Ni and Mo are all limited in terms of toughness. This C,
Regarding the contents of Ni and Mo, C: 0.01 to 0.15% by weight, Mo: 0.01 to 0.10% by weight, Ni: 1.4.
When the content is set to about 2.7% by weight, a weld metal having a high level of toughness can be obtained more reliably. From this point, C: 0.01 to 0.15% by weight, Mo: 0.01 to
It is desirable that the content be 0.10% by weight and Ni: 1.4 to 2.7% by weight (second invention).

FP is a value obtained from the above equation (1) and is an index of whether or not the weld metal is completely transformed into austenite during cooling. When the value of FP is 0 or more, it completely transforms into austenite, and the toughness of the weld metal can be further increased. If the value of FP is less than 0,
Complete transformation to austenite hardly occurs, and a little δ ferrite remains, so that the toughness of the weld metal tends to decrease. From such a point, it is desirable that FP be equal to or more than 0 (third invention).

[0035]

EXAMPLE As a flux cored wire for self-shielding welding, a wire prepared by filling a steel sheath with a flux and drawing it to a wire diameter of 1.4 mm was used.
The flux cored wire has five types of cross-sectional shapes shown in FIG. 1, and the flux cored wire of the type shown in FIG. 1 (C) was employed. Composition of the steel shell is C: 0.008% by weight, S
i: 0.008% by weight, Mn: 0.25% by weight, P:
An alloy containing 0.005% by weight and 0.005% by weight of S, with the balance being Fe was used.

Welding was performed using the above flux cored wire, and welding workability, porosity resistance and toughness of the weld metal were examined. At this time, the welding conditions shown in Table 1 were used. For the test piece, SM490B corresponding to JIS Z 3106
And using a plate having a thickness of 20 mm and a length of 500 mm,
Welded according to JIS Z 3111. The welding workability was evaluated by visually observing the stability of the arc during welding and the state of occurrence of spatter. The porosity resistance of the test piece after welding is based on JIS Z 3104
An X-ray transmission test was performed according to the above. The classification of one kind and one kind was defined as good (O), and the other classification was defined as poor (X).
The toughness of the weld metal was tested in accordance with JIS Z 3111.
Those having an impact value at 70 ° C of 70 J or more were evaluated as good.

The components of the flux cored wire are shown in Tables 2 and 3. Tables 4 and 5 show test results on the welding workability, the porosity and the toughness of the weld metal. As can be seen from these tables, the flux cored wire according to the embodiment of the present invention (No.
When 0) is used, welding workability, porosity resistance and toughness of the weld metal are all good. On the other hand, when the flux cored wires (Nos. 11 to 31) according to the comparative example were used, any of the welding workability, the porosity resistance, and the toughness of the weld metal was poor, and the overall judgment was made. X.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

[0041]

[Table 4]

[0042]

[Table 5]

[0043]

According to the flux cored wire for self-shielded welding according to the present invention, welding workability and porosity resistance are extremely improved, and a weld metal having high toughness can be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing types (five types) of cross-sectional shapes of a flux cored wire.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor, etc. Hatano, etc. 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Inside Kobe Research Institute, Kobe Steel Ltd. (72) Inventor Hiroyuki Morimoto Takatsuka, Nishi-ku, Kobe City, Hyogo Prefecture No. 1-5-5 Kobe Steel Works, Ltd. Kobe Research Institute F-term (reference) 4E084 BA03 BA04 BA05 BA06 BA09 BA10 BA16 BA17 BA18 CA03 CA16 CA21 CA24 CA25 DA14 GA02 HA01

Claims (3)

[Claims] 1. A flux cored wire for self-shielding welding in which a flux is filled in a steel sheath, C: 0.01 to 0.30% by weight, Si: 0.01 to 100% by weight based on the total weight of the wire. 0.30% by weight, Mn: 0.5
0 to 3.00% by weight, Mo: 0.001 to 0.25% by weight, Ni: 1.0 to 3.0% by weight, Al: 1.5 to 4.0%.
0% by weight, Mg: 0.5 to 2.0% by weight, Ca, Sr,
One or more of Ba: 3.0 to 7.0% by weight, L
Fluxco for self-shielding welding, characterized by containing i: 0.05 to 0.30% by weight, F: 0.5 to 3.0% by weight, and Ni / Mo: 10 to 300. Ardwire. 2. C: 0.01 to 0.15% by weight, Mo:
The flux cored wire for self-shielding welding according to claim 1, wherein the content is 0.01 to 0.10% by weight and Ni: 1.4 to 2.7% by weight. 3. The flux cored wire for self-shielding welding according to claim 1, wherein FP defined by the following formula (1) is 0 or more. FP = [C]-0.145 x [Si] + 0.013 x [Mn]-0.3 x [Al] + 0.196 x [Ni]-0.123 x [Mo] + 0.393 ------- Formula (1)